Technical Field
The disclosure relates to a communication device and a method for designing a multi-antenna system thereof.
Description of Related Art
Smart antenna design techniques capable of reconfiguring antenna patterns and the directions of radiation beams in response to environmental variations of the wireless communication channels are very important research topics in the field of antenna designs. If the antenna patterns and the directions of radiation beams can be steered toward the directions of transmitting or receiving energies of communication signals, the signal quality received by a receiver may be greatly improved, and the effective distance or coverage range of transmitters could also be increased.
In the prior pattern-switchable antenna techniques, if a lower frequency band is chosen for communication operations, the required overall physical size of antenna elements for multi-antenna systems would be too large for practical applications. For example, the operating wavelength of 700 MHz band for Long Term Evolution (LTE) system would be approximately 430 mm. Therefore, it's not an easy task for integrating several antenna elements for LTE700 operations into a single communication device simultaneously. On the other hands, prior active antenna array techniques would require to design feeding networks with high complexity and cost. For other prior pattern reconfigurable multi-antenna techniques, although complexity or cost of antenna feeding networks could also be reduced, these used multi-antenna elements would still occupy large areas when applied in lower frequency bands.